The present invention relates generally to a system and method for quickly discharging an alternating current (AC) relay. More specifically, the present invention relates to a system for minimizing the amount of time expended in discharging a direct current (DC) relay coil charged using an AC power source.
Relay coils are inductors and oppose changes in current flow. DC coils are often used within an AC relay to generate a switching force capable of actuating one or more load switches. In such case, an AC voltage is rectified and then applied to the DC coils which store the applied energy and generate the switching force. Once a voltage or energy threshold has been met, load switches are actuated by the switching force of the DC coil. As the supply voltage to the coil is switched off, high voltage peaks are generated due to the inductance of the coil. Such high voltage peaks can damage control logic, power sources and switch contacts.
AC relays often include rectifier circuits, such as full wave or half wave rectifier circuits, that convert AC voltage to DC voltage which is used to charge DC coils. A full wave rectifier circuit generally includes four diodes in a bridge configuration. In such case, a DC coil is often coupled across the diode bridge. After the DC coil has been sufficiently charged as to provide the switching force, the AC supply voltage is removed. The energy stored in the DC coil is dissipated by the diodes over a period of time. However, the period of time needed to dissipate the energy stored in the DC coil can be substantial.